The present invention relates to methods and apparatus for detecting cardiac repolarization abnormality.
Cardiac repolarization abnormality can be indicative of heart disease. In some cases, such as long QT syndrome, sudden cardiac death can be the first visible sign of such disease. Accordingly, cardiac repolarization has been studied to find a correlation between an electrocardiogram signal and an underlying heart disease of a patient. Conventional cardiac repolarization analyses often focus on the QT interval and/or the polarity of the T-wave.
Unfortunately, the cardiac repolarization process is very complex and thus the resulting portions of the electrocardiogram signal can be difficult to analyze. For example, it can be difficult to determine whether a change in the T-wave is due to onset of heart disease, due to alternative placement on the patient of the surface electrodes used to obtain the electrocardiogram signal, and/or due to noise (e.g., muscle noise). Interval analyses are limited in the detection of such changes and their sources. Also, measurement error of T-wave offset can affect both the sensitivity and the specificity of a particular application.